Method and apparatus for producing high vacuums.



W. GAEDE.

METHOD AND APPARATUS FOR PRODUCING HIGH VACUUMS.

APPLICATION FILED DEO.22,1909.

1,669,40, Patented Aug. 5, 1913.

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W. GAEDE.

METHOD AND APPARATUS FOR PRODUCING HIGH VAGUUMS.

APPLICATION FILED DEC. 22, 1909.

1,069,408 Patented Aug. 5, 1913.

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@M y W WOLFGANG GAElDE, OF FREIBURG, BRIEISGAU, GERMANY.

METHOD AND APPARATUS FOR PRODUCING. HIGH VAGUUMS.

Specification of Letters Patent.

Patented Aug. 5,1913.

Application filed December 22, 1909,. Serial No- 534,518.

To all whom it may concern Be it known that I, WOLFGANG GAEDE, a subject of the German Emperor, residing at Zasiusstrasse 43, Freiburg, Breisgau, Germany, have invented a certain new and Improved Method and Apparatus for Producing High Vacuums; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

My invention relates to a method and apparatus for producing high vacuums. All pumps hitherto known and in use for this purpose act according to the principle that the receiver or vessel that is to be evacuated is periodically connected with a chamber whose capacity is capable of enlargement, such as the cylinder of a piston pump or the buckets of a mercury pump. Contrary to this principle I employ the friction of the gas on solid surfaces and its internal friction for ant-raining it in the desired direction, that is to say, to make it flow out or away. from the receiver and be discharged into the atmosphere.

According to this manner of proceeding, my invention broadly consists in the methodof establishing a moderate initial vacuum between two substantially parallel smooth solid surfacesand rapidly moving the one surface with relation to the other in the direction of their tangent, by which means the gas filling the space between the two said surfaces is entrained in the direction of the motion of the solid surface and thus can be discharged through suitably arranged ports.

In the drawing Figure 1 is a diagrammatic section of a device representing the simplest form of pump according to my invention. Fig. 2 is a sectional elevation on line 22 of Figs. 3 and 4: of an embodiment of my invention showingthe form preferred for the production of high vacuums. Fig. 3 is a sectional elevation on line 3-3 of Fig. 2 and Fig. A a plan View of the pump illustrated in the two preceding figures. Fig. 5

illustrates the combination of my improved pump with a suitable receiver and a preliminary pump, for the production of high vacuums, as hereinafter described.

In Fig. 1 of the accompanying drawings A is a cylinder which rotates on a shaft B.

C is a stationary casing with a cylindrical bore in which the cylinder A fits as tightly as is compatible with easy rotation. D is a groove cut in the casing concentrically wit-h the cylinder A. At one part the groove D is blocked by a plug E and on each side of this plug an admission pipe F and a discharge pipe G open into the groove. The groove D may be filled with air and the pipes F and G may be in free communication with the atmosphere. When the cylinder A is rotated in the direction of the arrow the air in the groove is carried with it owing to. the friction between the air and the pe riphery of the cylinder. The deeper the groove in the radial direction, the more air is carried around with the cylinder and since the clearance between the surface of the latter and the plug E is smaller than the depth of the groove the air is dammed at G; or if the pipes F and G are, as is assumed, in free connection with the atmosphere, air is drawn in at F and delivered at G. Instead of air any other suitable gas can be conveyed in this manner.

The pump according to my invention is especially suitable for producing high vacuums. Since the coefficient of internal friction of gases is independent of the pressure when other conditions are constant, the difference of the pressure in front of and behind the pump is invariable within very wide limits for all pressures. If therefore the pump is so proportioned that at a certain number of revolutions it produces a difference of pressure of, for instance, 6 centimeters mercury, it would reduce the pressure in the receiver only to 7 0 centimeters if it worked against atmospheric pressure of 76 centimeters. If, however, it is connected up behind a preliminary pump which establishes an initial vacuum of 10 centimeters then a final vacuum of 4; centimeters is obtained. As the initial rarefication proceeds this rule does not hold good, but I have found by experiments that very high vacuums can be obtained with a preliminary vacuum of about 1 millimeter.

In Figs. 2 to 4 a construction of the pump is shown which is suitable for producing very high vacuums. On a shaft B is keyed a cylinder A, in the periphery of which are nine flanges D" forming eight deep grooves. Any number of flanges and grooves might be employed the number shown in the drawing being chosen'merely by way of an example. The cylinder is surrounded by an airtight casing C containing bearings for the shaft 13 provided with ring lubricators R. The cylinder A fits the pasing C at its periphery as closely as ossible without contact. On the upper si e of the casing O is a plug E which is formed of separate blades forming a comb and severall entering the respective grooves between t e flanges D, each blade fitting its groove as tightly as possible without touching the cylinder, On each side of the plug are ports f and 9 (Fig. 2) in the casing for conveying the air from the grooves to various ducts f f g 9 provided in a block H screwed to the casing said ducts connecting ports F and Gwith the various grooves. In Fig. 4 a plan of the ducts in the plane 4-4 of Fig. 2 is shown in dotted lines. The discharge port g of the central groove is connected b the ducts J J with the suction ports f f: of the outer grooves. F is connected with f and G with g 9 That is to say the central grooves are connected in series with the outer grooves, whereby nearly double the pressure eflectis obtained as compared with parallel connections.

In Fig. 5 my vacuum pump is shown fitted up for use. X is the friction pump con structed according to Figs. 2 to 4:. L is an ordinary vacuum pump used as a preliminary pump, in the illustrated instance a rotary piston pump of a well known type, but which may be any suitable air pump capable of producing a preliminary vacuum of about 1 millimeter mercury; Z is a high speed electric motor and H is a receiver representing the vessel that is to be evacuated. The receiver H is connected by a pipe to the suction port F of the friction pump and the discharge port G of the latter is connected by another pipe to the suction port of the preliminary pump L. The discharge port of the latteropens freely into the atmosphere. Suitable sheaves are provided on the shaft of the electromotor Z and the two pumps L and X respectively and are connected by belting capable of driving the friction pump at a very high rate of speed and the preliminary pump at a speed adequate to establish an initial vacuum of about .1 millimeter mercury in the friction pump and in the receiver.

To operate the system the electromotor is I started. The pressure in the system quickly decreases as the preliminary pump exhausts the air from the friction pump and the rein the receiver in a very short time. The actual height of the vacuum obtained, other circumstances being equal, depends, more upon the speed at which the fraction pump is driven, than on the height of the initial vacuum. With a speed not exceeding 8,000 revolutions per minute the highest hitherto known vacuums are produced.

It is a specific and important advantage of my improved method and apparatus that neither mercury vapor nor oil vapor are formed in the vacuum produced.

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is 1. The method of producing high vacuums, which consists in producing a moderate vacuum, and entraining the gas in that vacuum by a rapidly moving solid surface, in a tangent substantially parallel to that of the surface.

2. In a high vacuum apparatus, the combination of a rotary friction pump comprising a rotary member and a stationary member in the path of the gas entrained by the periphery of the rotary member on the rapid rotation of the same in a tangent substantially parallel to that of the surface, with vacuum producing means other than the friction pump for producing an initial vacuum in the friction pump, whereby the gas exhausted to a moderate vacuum by said vacuum producing means is acted uponby the friction pump to produce very high vacuums.

3. In apparatus for producing high vacuums, the combination with a friction pump consisting of a substantially cylindrical body adapted to be rapidly rotated in a stationary casing, grooves in the circumference of the said cylindrical body, a suction and a discharge port in the casing, projections in the casing located between said suction and discharge ports and adapted to approximately fill said grooves in said rotary cylindrical body', of means other than the friction pump for producing an initial vacuum in the friction pump, whereby the gas exhausted to moderate vacuum by said vacuum producing means is acted upon by the friction pump to produce very high vacuums.

4. In apparatus for producing high vacuums, the combination with a friction pump consisting of a substantially cylindrical body adapted to be rapidly rotated in a likewise substantially cyllndrical casing, grooves in ducing an initial vacuum in the friction pump, whereby the gas exhausted to moderate vacuum by said vacuum producing. means is acted upon by the friction pump to produce very high vacuums.

5. In apparatus for producing high vacuums, the combination with a friction pump consisting of a substantially cylindrical body, a substantially cylindrical stationary casing surroundin said body, means for rapidly rotating said body in said casing, grooves in the circumference of said rotary cylindrical body, projections in said casing shaped and dimensioned to fill one portion of said grooves, stationary channels in said casing connecting points of outwardly located grooves and points 'of inwardly located grooves at opposite ends of said projections, a suction port in said casing connected to the channels leading to the inwardly located grooves, and a discharge port connected to the channels leading to the outwardly located grooves, of means other than the friction pump for producing an initial vacuum in the friction pump, whereby the gas exhausted to moderate vacuum by said vacuum producing means is acted upon by the friction pump to produce very high vacuums.

6. In apparatus for producing high vacuums, the combination of a friction pump consisting of a rotatable body, grooves therein, a casing for the same, discharge and suction ports for the casing, projections thereon, channels in said casing, connecting points in proximity to either end of said projections so as to connect the sections of the grooves not filled by the projections in series between the suction and discharge ports, and means other than the friction pump for producing an initial vacuum in the friction pump, whereby the gas exhausted to moderate vacuum by said vacuum producing means is acted upon by the friction pump to produce very high vacuums.

In testimony, that I claim the foregoing as my invention, I have signed my name in presence of two subscribing witnesses.

WOLFGANG GrAEDE.

Witnesses:

HERMANN VON DEOHEND, GEORG STROHMENGER. 

